1. Field of the Invention
The present invention relates to an image reading apparatus, an image forming apparatus, an image reading method and a computer readable information recording medium.
2. Description of the Related Art
In a case where a scanner part of a MultiFunction Peripheral (MFP) reads an original, improvement of the specification of the reading speed is demanded. When an original is read, processes are carried out, i.e., the image of the original is read by the scanner part, an image processing part carries out image processing and compresses the thus obtained image, and a controller stores the thus processed image in a secondary storage device such as a HDD. It is necessary to carry out the flow of the sequence of these processes within a short period of time.
For example, in such a MFP, a technology is already put into practice. In the technology, in order to reduce a period of time required for reading both sides of an original, the both sides of the original are read simultaneously, and the thus obtained image data is stored in a page memory. Thereafter, the images are read from the page memory for the respective sides of the original, side by side. Then, image processing is carried out on the thus read images by the image processing part, and the controller carries out subsequent processes.
In such a MFP that can carry out reading both sides of an original simultaneously, there is a case where a sensor used for reading the front side and a sensor used for reading the back side are different. In this case, because of a difference between the respective image reading devices for the front side and the back side, a processing parameter(s) used for shading correction (white level correction), black correction (black level correction) and/or the like is(are) different between the processing for the front side and the processing for the back side. Thus, it is necessary to change the processing parameter(s) depending on image data of the front side and image data of the back side.
For this purpose, the image processing part reads the processing parameter(s) from the page memory, and carries out image processing using the thus obtained processing parameter(s). As a specific procedure, first, original images are read, and are stored in the page memory. In parallel to the image reading operation, an image transfer instruction is provided for transferring the front side of the read image from the page memory to the image processing part. Based on the image transfer instruction, the processing parameter(s) for the front side is(are) read out from the page memory, and the image processing part obtains the read processing parameter(s). Thereafter, the front side of the read image is read out from the page memory, is transferred to the image processing part, the image processing part carries out image processing using the processing parameter(s) for the front side that has(have) been previously obtained, and outputs the processing result.
Thereafter, for the back side, in the same or a similar procedure, an image transfer instruction is provided, and the processing parameter(s) for the back side is(are) transmitted to the image processing part. The image processing part thus obtains the processing parameter(s) for the back side as a substitute for the processing parameter(s) for the front side that has been stored. After the read image of the back side is transferred to the image processing part, the image processing part carries out image processing using the obtained processing parameter(s) for the back side, and outputs the processing result.
However, the period of time required for obtaining the processing parameter(s) is fixed. Thus, a reduction of the period of time required from the reading of an original(s) to the outputting has limitations even when the reading of the original images, the image processing by the image processing part, the processes from the compressing of the image data to the storing of the image data in the secondary storage device are speeded up. That is, there may be a problem of the period of time required for obtaining the processing parameter(s) as a bottleneck although the reading speed is improved by scanning both sides simultaneously.
In order to solve the problem, a technology is already known in which image data of two sheets of originals is stored in a page memory, and the number of times of switching the parameter(s) is halved. Specifically, a low resolution mode is provided in which an image is read in a resolution lower than the related art. In the usual mode, image data of the front and back sides of one sheet is stored in the page memory. In contrast thereto, in the low resolution mode, image data of the front and back sides of two sheets is stored in the page memory. Then, after the processing parameter(s) for the front side is(are) obtained, the read image of the front side of the first sheet is transferred, subsequently the read image of the front side of the second sheet is transferred, and image processing is carried out. After the image data of the front sides of the two sheets are thus transferred, the processing parameter(s) for the back side is(are) obtained, the read image of the back side of the first sheet is transferred, subsequently the read image of the back side of the second sheet is transferred, and image processing is carried out. Thus, the read images of the two sheets of the originals are transferred in the order of: the front side, the front side, the back side and then, the back side. Thus, only the two times of obtaining the processing parameter(s) are required in this technology whereas the four times of obtaining the processing parameter(s) are required in the related art. Thus, it is possible to reduce the number of times of switching the processing parameter(s) (see Patent Reference No. 1 (Japanese Laid-Open Patent Application No. 2010-34751).
However, according to this technology of Patent Reference No. 1, in a case where a user does not wish the low resolution mode, the read image of the front side of the first sheet is transferred after the processing parameter(s) for the front side is(are) obtained, and then, the read image of the back side is transferred after the processing parameter(s) for the back side is(are) obtained, as in the related art. Thus, in this case, the same as in the related art, the transfer of the read image is carried out after the processing parameter(s) is(are) obtained, and thus, it is not possible to reduce the period of time required from the image reading to the outputting.